Apparatus for expanding and compressing gases.



No. L784. Patented Nov. :3; I900.

L. ALLE N. APPARATUS FOR EXP'ANDINGAND COMPRESSING GASES.

(Application flledMar. 28, 1899.)

.(No mm.)

vs PETERS c0. FNOYO- w the borough of Bronx, city of New York, and

. reciprocation of a piston therein, the volumes UNITED- STATES lATENT 6FFICE.

LEICESTER ALLEN, O l NEW YORK, N. Y.

APPARATUS FOR EXPANDING gAND COMPRESSING GASES.

SPECIFICATION forming part of Letters Patent N 0. 661,7 dafd November 1900- Application filed March 23. 1899.

To all], whom it may concern} Be it known that I, LEICESTER ALLEN, of

State of New York, have invented an Improved Apparatus for Expanding and Compressing Gases and Vapors for Use in Refrigeration and for other Purposes; and I do hereby declare the following to be a full, clear, and exact description of my invention, reference being had to the accompanying drawings, forming part of this specification.

My invention partly relates to means for effecting that kind of expansion or compression known in the art as stage expansion or compression and in which the gas or vapor is not expanded or compressed by one continuous expansion or by one continuous compression, but in which the gas or vapor is expanded or compressed in and by separate and consecutiveoperations to different pressures or stages of expansion or compression either with or without intermediate heating or cooling, such intermediate heating or cooling when used being ordinarily effected by passing the gas or vapor after partial expansion or compression through a heating or cooling medium or over a heated or cooled surface.

Hitherto diiferent stages of expansion or compression have been for the most part attained in separate expansion-engine cylinders or compression-engine cylinders by the of gas or vapor admitted to and discharged from such cylinders being controlled either by automatic or positively-actuated valves or in some instances by both positively-actuated and automatic valves.

My in vention partly relates to the cylinders and heads of cylinders of engines used in the expansion and compression of gases and vapors,which engine-cylinders and engines may at will be employed either for expansion or compression.

My invention also relates to certain combinations of,one or more cylinders comprising my improvements with an engine-cylinder of a hitherto commonly used type for a purpose hereinafter specified.

In an apparatus embodying my invention the volumes and pressures of gases or vapors are changed in stages in an engine-cylinder serial No. 710,853. (No model having a reciprocating piston and equal and. uniform stroke displacement and having a larger clearance connected with the highpressure space than that connected with the low-pressure space therein, the clearance connected with the low-pressure space being chosen arbitrarily and the clearance connected with the high-pressure space being a mathematical function of the clearance connected with the low-pressu re space and computed therefrom, as hereinafter set forth, the function of said apparatus specifically consisting in inducting to such a cylinder on one side of said piston the volume of gas or vapor which it is desired to change to another specific pressure and volume, effecting a part of such change during the completion of the stroke of the piston after the said induction, exhausting or discharging the so partially changed volume from the cylinder and from the space therein on that side of the piston wherein the partial change has been effected,

inducting the so exhausted or discharged volume to the space on the other side of said piston,and there effecting still another-change of pressure and volume during the movement of the piston in a direction opposite to that by which the first change of volume and pressure was effected, substantially as hereinafter more fully set forth.

The apparatus may be used solely and separately for effecting a given total change of pressure and volume of a gas or vapor, or it may be used in combination with previouslyemployed methods.

My improved apparatus consist-s, partly, in an engine-cylinder forexpanding or com pressing gases or vapors into which predetermined different volumes but equal weights of a gas or vapor are respectively inducted on opposite sides of a piston reciprocating in said cylinder, the end clearance connected with the low-pressure space of which is chosen arbitrarily by its designer or constructor, while the end clearance on the high-pressure side of said piston is made larger and its content computed as a mathematical function of the arbitrarilyassumed clearance on the lowpressure side, as hereinafter described, the high-pressure space and the low-pressure space separated by said piston being connected by a valve-controlled passage.

heads,valve chests,valves,and generally all its.

appurtenances except the piston and pistonrod and the heat-insulating material or materials with which it may be enveloped. Lwill.

also use the term end clearance toindicate.

all the continuous space or volume whichat the beginning of the stroke. oh the piston. is comprised in and included by the cavities cona nected directly or indirectly with the space lying between the. piston, and thecylinde gs head nearest to the. piston. I will also em; ploy the term stroke; displacement toin; dicateavolume of gas o vapor displacedby the movementof thepistonfrom the body of, thecylinder or its. iHFBIiQ T or a. geometrical volume equal to the volume described by the.

advancing: face of the piston during asingle stroke. 1 also mean by the words equal; stroke displacement such substantially equal stroke displacement, as is commonly ef; fected in double-acting reciprocating engines. having ordinarily-used sizes of piston-rods,

the voljumeof the pistomroditself. being, so

small in comparison. With the volume. de; scribed during the stroke by the,adya,ncing.i

e fac of e p t n. Opp si at-face whichisdirectly adjacent to. the. piston rod. us y to p c n. neqnali y t ceeding from three tofoun per cent, of the.

volume described bysaid free face. I will ymalse use the term valve-contnolled passage to indicate a passageor duct for. theinduo.

tionpr eduction of gas. or vapor intoor out,

of the body of. the cylinder, on both. intoor. out of the same, the time andjquantityojfsuch,

. induction or. eduction being regulatedbyany spaceand low-pressure. space are, each conkind of valvefamiliallito engineers or which maybe hereafter produced. I will also disr. ting uish the spaces in. an engine; cylinder situated on opposite sides of a recipnocating.

piston, to oneof which agasor vapor isi n ducted at higher pressure than the. gas. or.

vapor is inducted tothe other, respectively, as. the high-pnessure spaceand the low-pnes,-,.

sure space, the. term high pressnre space.

meaning thespace to which the gas or vapor.

at the higher pressureis inducted and; the. term low-pressure. space meaning the.

space into Whichthe gas. or, vapor is inducted} atalower pressure. The saidhigh-pressune.

sidered hexgeinas exclusive of the end-clear:

w pac and "a he r. xi uml c iequal th m e disp acem t They. ay her fore be properly characterizedas ah inclosed ar ab is -p es uwspws se a a et e lelo nrsss re p 9 eparated from each otherby a movable septum. The septum may-be eithenapistonloi aiflexible diaphragm; but for purposes of this specification it will be described .as a piston.

In this specification I will also hereinafter use the word gas as inclusive in its mean- ;ingofi all. vaporsor mixtures of gases or vapors or mixtures of the same with some percentage of the. liquids from which they are" generated.

Figure l in the drawings illustrates the construction ofa single engine-cylinder and its heads as used by me in my invention for canrying-outtwo. separate stages of expansion or compression, the drawing being a section taken on the, lineal a; in Fig. 2,- I is a pa tial detailed view of the inside of one Ofi h 'hea s'q the. cy inde w fiit Fig; 1, showing. novel; features, of construction .hi ge e -ea tc y n ention... E s- 3 sv a. vertical section throughian engineecvlinden Qn irJmted similafi y. o a shown nt l a.

1, but l1ay,ing. a somewhat-inedified. form of ead. aidl l mughann he si eot ordin ry ype, he. wo. y i d rs-b ng in n such manner to, carry out three separate stagesofi. expansion or compression. Eig t is apantialoutsidevievsgof the modifiedforin oficylinder-head justmentioned above. Rigs. 5 an d 6 are diagrams used to illustrate the. ture n r ults i -mi ed. y my mp ve appar tus. hey ar of t e nat r iegrams bt n d, y he us of. the WQ -kIiQWn s eamnd ca es;b t mall s n a lew e 1'.- osses by, t on o hea nt rcha hey a nt i' ate y ndicate onl h i l result sjrathenthan the actual resultswhich a e attaine p ac i B,eferriugv new todrajngs, Figs. 1. and. 3, heqy nde ieae Whe 'einI Q a at a distinct expansions or compressions of the mewe s t s m y-be pQ 0r 'ne n bered 1 in Figs. 1 and 3, the high-pressu re.

,spacedn eachofthese cylindersbeing. shown a set he-, ieht t ni wnand e P s n.

eing. hown s a ns just. mp e stroke, displacement, In these figures the.

pistonsofi the cyliuders lare indicated bythe numeral.z thepiston rods. by. 3,- those cylin- ,den-headsgighiehcomprise a part of my invention by 4:, thosemeadswhich do not comprise any pai;t,of myinvention by 5, andlthe,stu ffing-boxes by b. The piston-rod 3 isinpractice connected byv intermediate mechanism with-the crank-of. any-wheel shaft, which by ,stored energy will move the. piston during ,transfer. of. gas from either of the spaces to,

it hespaeeon. the other sideofthe pisten and ;Will also regulate the movement of thepiston.

during other periods of thestroke; but as. a fly;w heel an il-theconnectionsof the same to thepiston rod constitute no part of niy invention.they are, omitted in the drawings, and as they are old and familiar devices in the iart itis v un necessary tofurtherdescribe them. Eachofithe cylinders in,which term, as

Labove, explained, the headset. the cylinders Fig. 2"

are included-has different end clearances, that end clearance connected with the highpressure space being greater than that connected with the low-pressure space, but being at the same time a function of that connected with the low-pressure space. This relation between the end clearances of the cyl inders, in which two stages of expansion or compression are performed, is essential to the accurate operation of the apparatus, and the clearance connected with the low-pressu re space being arbitrarily assumed the clearance connected with the high-pressu re space is accurately computed by the formula given below, wherein the clearances are expressed as fractions or percentages of the stroke displacement and the stroke displacement is taken as a unit of volume. The formula for computing the clearance on the high-pressure side is derived from the followingalgebraic equations, which also supply the needed formulae for determining in advance the points of cut-off and of exhaust opening and closure.

The notation used in the formulae and the equations which follow is considered as being for expansionof gases and vapors; but when the apparatus is used for compression the clearance connected with the high-pressure space is the same as when it is used for expansion and is computed precisely as though the apparatus were to be used solely for expansion. When the ratio of compression in the low-pressure space is the reciprocal of that employed in expansion, the volume inducted to the low-pressure space for compression will be exactly the same as the volume discharged from the same space after final expansion.

Notation.

'0 equals the stroke displacement, (represented in the diagrams, Figs. 6 and 7, by abscissas 'v,) the stroke displacement being taken as the unit of volume.

'0, equals the volume delivered from the low-pressure space after the second stage of expansion has been performed.

o equals the yolume inducted to the lowpressure space, and consequently the volume delivered from the high-pressure space after the first partial expansion.

o equals the volume inducted to the highpressure space before the first stage of expansion.

(J equals the arbitrary clearance connected with the low-pressu re space and expressed as a fraction of the stroke displacement o. This arbitrary clearance should be the minimum practically possible to attain best re sults.

m equals the clearance connected with the high-pressure space, also expressed as a fraction of the stroke displacemento and to be computed for each case.

29 19 1), equal respective symbols for high, intermediate, and lowest'pressures in the order named.

R equals the ratio o /o corresponding to the ratio 19 /19,, and found for air bythe formulap o pgv or found for steam by the formula p v p vg the value of it? for air being 1.41, and the value of m for saturated steam containing no water when inducted being 1.134, which is a mean value for different pressures.

R equals the ratio o /o corresponding to the ratio 19 /19,, and computed in the same way as directed for R The stroke displacement being taken as unit of volume and the clearance represented by C, the entire contents of the low-pressure space, together with the clearance connected therewith, is equal to 1+0. The exhaust closure is elfected, as hereinafter explained, at a point of the stroke such that the gas retained in the cylinder by the closure will at the completion of the stroke be compressed in the clearance in the ratio R or to a pressure substantially equal to the maximum pressure in said space. Consequently the volume 1: that will be delivered from the lowpressure space will be the entire volume 1+0 less R C. From this reasoning is derived Equation 1.

We may write the following equations: t :l+C-R O.... (1) o :(l|GR,C)IR (2) w:(1o )Z-(R 1) 4 As the volume o delivered from the 10wpressurespaceis equalto theinducted volume 0 multiplied by the ratio R,, we find 12 by simply dividing the volume o =1+G R O by E and thus we derive Equation... 2, which expresses the value o or the volume inducted to the low-pressure space, which is. of course also the volume discharged from" the high-pressure space, and as this volume 41 is equal to the volume inducted to the high-pressure space multiplied by the ratio R, (which is the ratio of expansion in the high-pressure space) the volume 11 will be the volume (l+OR C)+R R and thus we derive Equation 3'. Lastly. :0 representing the clearness on the high-pressure side it is clear that the stroke displacement plus this clearance is the total volume of the highpressure space, together with the clearance connected therewith, and as l'v. +.9c equals the volume that must remain in the highpressure space and the clearance 33, connected therewith, and as in order that this shall fill the clearance space at the highest pressure it must be compressed to the volume 2)+( 2* )7 which shows the derivation of Equation 1.

alsoa fiunction of O. Thevalues of 0 '0 and 11 having been found in terms ofv stroke dis.- placement, if the latter berepresented byan abscissa having. a length equal, to the length. of the stroke drawn to any convenient scalethesaid values. become formulae for determining the pointsof cut-off, exhaustopening and closure, &c.

Whentheratio of the changeofz pressure effected in the machine is. comparatively small-and is alsoalike inboth the high and& low pressurespaces, the,clearanceconnected:

with the highrpressurespace. islargeimproportiomto the strokedisplacement,,evenwhen thearbitrary clearance connected with the low-pressure spaceis av small fractionof: the strokedisplacement; but with. thearbitrary.

clearance connected with: the low-pressure spaceremaining constant the clearance.con-. nectedwith the high;pressurespace requires to be smaller as the ratios of change of pressures increase andalso when the ratioof pressure change inthe high-pressure spaceis less than that. in.thelow-pressurespace. When o /19 :4. and p 9 ,=2 and the arbitrary clearance is four pen cent. ofthestroke displacement, the clearance connected with the high-pressure space isfound. by theformula displacement. When p /p =6 and:p /p =3 and the arbitrary clearance is four per cent. of the stroke displacement, the clearance connected; with the high-pressurezspace requires 4o to beaboutseventeen percent.

When intermediate heating or cooling. is

employed, thevalue of. k orof min the-for-.. mulafor: finding therelative pressures and.

volumesincreases or diminishes by an amount corresponding to the temperature. change so effected. The temperatures respectively taken before and after such heat change is efiected are theadditional dataneeded for detel-mining the relative pressures and volumes.

or less modified for the inducted volumes, the.

extent of such modificationbeing determined from the resulting temperatures so produced.

In order that a machine of this kind having a given stroke displacement and givenarbitrary clearance connected with the lowpressure space may be readily employed. for

ance. ume. is subtracted from thepreviously-existthis feature broadly, not rigidly confining myself to theprecise mechanistmor-either of the two modifications of mechanism forv this purpose which I willnow proceed to describe.

Ineach of the heads 4,which,with.thebodies of. the'cylinders to .which theyare fitted and pistonswonking insaidcylinders, inclose the high-pressure spaces I form chambers '7- of ,fixed. capacity, these chambers. beingpartly IShOWIl .insection in Fig. 1 and in dotted outline inliigs. 1;, 2, and 4-. Therearesix of these chambersin theexample ofa two-stage ex pan.- sionon compressioncylinder shown iniFig. 1 land fourv in the two-stage expansion or compressioncylinder showninllig. 3. Thenumber of'these chambers should: besufficient: to

enabletheclearance connectedswith the high.-

pressure spaceto-beadjusted, as hereinafter described, to anypercentage of; the stroke displacement between the minimum and. maxi.- mum percentage of clearance tor which. the machine is-designed; Thus if-- the minimum clearance. connected with. the highpressure space which the machine is designed to ha.v.e

that is to say, the volumecontained between. ithepiston at the end of the stroke toward the givenito be about sixteen percent. of the stroke K said head; plus the volume contained in the .ports betweenthe valves and-the pistonon the same side-is eight per cent. of; the stroke displacement and the maximum clearance on enough of these chamber-s.when.used in conjunction with another. feature ofrconstruction described. farthenonto permit adj ustment of the clearance to any-percentageor fraction of the strokedisplacement between said. maximurn.and minimum.

- Each ofthe chambers 7. isprovided'W-ith a hole 8, placed as nearly aspracticableat the lower partrof said-chamber. When this-hole is opened, the volume contained by the chamber is added to the previously-existin g clear- When the hole is closed, the same voling clearance. These holes may be closed or opened by inserting-into them or taking out fromthem. screw-plugs 8'; but I prefer to provide for closingor opening them by supplying each with a'screw-valve 8?, Fig. 1, which has its threaded portion in the exterior shell of the head and a squared end extending out from the shell, which end: may-be engaged by an ordinary wrench or. spanner. The inner end ofthevalve is fitted tothehole bygrinding or packing to make itgas-tight. As these valves are in general to. be rarely used, the

construction described is preferred: onaccount of its cheapness; but itis obvious that a screvi valve constructed in a manner an alogous to the ordinaryglobe-valve and having a packed stem may be substituted in a machine desired to frequently change its range of pressures in the high -pressure space. When screw-valves 8 are used and when they are taken out, the screw-holes in the outer shell of the head are stopped with a screwplug, a portion of the thread into which the screw-plug is fitted having a tapered thread, as in the ordinary manner of plugging a hole gas-tight in metal.

If the minimum normal clearance be ten per cent. and the maximum clearance designed for the high-pressure space be sixty per cent. of the stroke displacement, the chambers 7 in a single head may together contain a volume equal to fifty-four per cent. of such stroke displacement. If there be six of these chambers of substantially equal capacity, as shown in Fig.1,theywould,0n the above assumption, if of equal capacity, each contain, approximately, nine per cent. of the stroke displace-- ment. This would alone permit adjustment to seven different clearances-to wit, the normal mini mum of ten per cent.with six additions of substantially nine per cent. each. It is, however, difficult to core outacasting with such precision as to give complete accuracy to these fractional clearances, and it is, moreover, necessary to provide for allintermediate fractional clearances in order to carry out the operation of the apparatus for different stages of compression or expansion in one and the same apparatus and with assured results. I therefore provide each cylinder-head adjacent to a high-pressure space with an additional device for this purpose. I construct in each of said heads one or more cylinders 9, Figs. 1, 2, and 3, ground or bored on the interior to accurate cylindrical form, and I fitin each, accurately and gas-tight, a movable piston-plug 10. Such piston-plug is forced toward the highpressure space in the body of the cylinder and held in position in one direction bya screw 11, which passes through a threaded hole in the exterior shell of the head, as shown in Figs. 1, 2, 3, and 4. As the piston is gas-tight, the screw 11 is not required to fit perfectly tight. It needs to be a good working fit, however, and it may be held from moving after adjustment by a jam-nut 12. The outer end of the screw may be formed with an eye, as shown, by which means it may be turned for adjustment, and which also affords a convenient at.- tachment for the hook of a tackle when removing the head. The piston-plug will be pressed firmly against the inner end of the screwin any position of the latter by the pressure of the gas in the high-pressure space of the cylinder. I prefer to make the axes of these cylinders parallel to the axes of the engine-cylinders 1;. but this requirement is by no means essential. There may be more than one of these cylinders and plug-pistons in a cylinder-head, as shown in Fig. 3. The capacity of such cylinder when there is only one should be, preferably, a little more than the calculated vapacityoi' one of the chambers 7,

or if more than one of them be employ ed their combined capacity when the piston-plug is pressed out by the gas in the cylinder as far as the construction will permit should be, preferably, a little more than the calculated capacity of a single chamber 7.

It is evident that by the adjustment of the regulating screw or screws 11 the clearance can be increased by any desired fraction of the capacity of the piston-plugged cylinder or cylinders 9. By the employment of these cylin- 8o ders and their pistons in conjunction with the chambers 7 a clearance which is any desired fraction of the stroke displacement within the maximum and minimum limits of clearance for which the machine is designed may be secured. This adjustment of the clearance serves also another useful purpose. In a heat-engine which converts heat into work by expanding gaseous bodies and applying the work exteriorly to the expanding body a clearance space which is connected with the space in an outer exhaust-port is a source of loss of work, because during the exhaust the metal inclosing the clearance cools and imparts heat to the outflowing gaseous body, 5 which heat cannot thereafter be directly recovered. and again applied to work; but in a compound, triple, or quadruple expansion engine having only one outer exhaust the exhaust from the cylinder or cylinders carry- I00 ing the higher pressure leads tothe induction-ports of those carrying lower pressures. Therefore although the metal inclosingclearance connected with a high-pressure space imparts heat to the outflowing gaseous body :05 in the same way as it does to a finally exhausted gas this heat is not wasted, because it increases the pressure or volume of the gas inducted to the next cylinder, where its expansive force is again exerted. This fact Ho causes the compound or multiple expansion system to utilize more of the expansive force of the primarily-contained heat than can be utilized in a single-expansion engine. As. yet the exact amount of heat that is transr15 ferred from the metal inclosing the clearance during exhaust and from the metal of the body of the cylinder during the exhaust period has not been expressed in mathematical formulae convenient and available for general use in designing engines, and hence to obtain the greatest exactness in the operation of such engines it may be necessary to alter the clearances as well as the valve-setting. Such adjustment and alteration of I25 clearances may be readily effected by the employment of my invention herein described.

In the operation of the apparatus the heat given off to the outflowing gaseous bodies from the metal inclosing the high-pressure 1 0 spaces is utilized in the spaces having lower pressure in the same way as in ordinary multiple expansion.

In Fig. 1 I have illustrated a double expani completed its stroke.

sionorcompressionengine-cylinder. When used for expansion, the gas to be expanded is first inducted to the high-pressure chamber or chest 13 through the opening. 14, thence 5 it passes through theinduction-valve 15 into.

the cylinder 1, and the admission being out off by the said valve when the proper volume. has been admitted it thereafter expands be.- hind the advancing piston till the. latter'has The eduction-valve 16 then opens and the gas, having expanded through its first stage, enters. the valve-con,- trolled duct or passage 17, .which leadsitothe. low-pressure space on the other sideof the 15 piston, the valve 18 performing the function 20 closure of the valve 18.

go-cating. piston-rod and its connection tothe 1.) opens and allows the gasnow-expanded;

through two stages to pass out. These operations continuously succeed. each other in, the regular Working of the engine, the power developedv being applied, through, the reciproperformance of exterior work. The exhaust closure in eachof thehi-gh and low pressure .spa,ces ismade at a point, such, as will retain in thecylinder sufficient gas tofiilthe clear- 5 anceconnectedwithsucltspace.with gassub.

stantially at the, highest pressure realized thenein. The heat which passes fnom the metal inelosing thecleara nee into the gas on vapor d uring the exhaust is thusrestored, to.

the metal before any more gas is indncted,

so, that in,case aliquefiable gasis used, there will: not be any material initialeondensation in, the clearances, and if, as is usual, the cylinderv and its heads be covered with a sub.-

5 stance which, much; resists the passage, ofi

heat there will be only a, very minute loss through the inclosing metal, Eachof the cylinders], Figs. 1 andv 3, operatesforexpan: sion, in, the same manner, thei-nd uction and;

ed,u ctipn valves. being indicated, by the same numbers used in the same, order as those-by which the valves in. Fig-. 1 are indicated.

When. the same cylindersare usedfor coma pression, the gas is inducted to each of them,

5 primarilynat andthroughtheval-ve 1,9, and

13 and outthrough thevopening 14.

its course. through any one of; the said, cylindersds exactly the reverse ofi that described; for: expansion, itsfinat issue from, the cylinden being through the. valve 15 into the chest I ll casethe gas instead of performing exterior Work through the medium ot the piston-rod;

has work performed upon, i ,t by exterionpovver applied to the piston-rod, andthevalve-gearand valves must be adjusted; to, open: the

valves at the same place where they close for they would open for expansion.

When the machine is used, for a compressor, a volume substantially equal to that of the stroke displacement is inducted to the lowpressure. space, the induction valve being then closed. The piston, which has now made a f:ull=stroke, makes a return stroke, com pressingvthe confined gas to the first stage. Thereupon the discharge-valve on the low-pressu re side oi the piston andtheinduct-ion-valve on the high-pressure side open simultaneously and the. gas, compressed; to its first stage is transferred by the, remainder of the stroke to the high-pressure space through, the valvecontrolled; passage. The. gas having been so transferred both, the dischange-valve ot the low-pressure side and, the induction valve. ot the.high-pressureside are closed, and the discharge-valve, of; the high pnessure. side re- A mainsiclosed. The piston then, m akesva third; stroke,:,tgai n ind uetinga volume substantially equal; to th eistrokedisplacement into the lowpressurespace,and;at the sameti meicom pressing. the; volumeconfined in, the high-pressure the point fixed. for discha-rge firon r, the high.- pressure space, the, discharge-valve of the shre ess re na is opene a l e end, clearance. This series. ofi actions being repeated indefinitely the tnansfer ed com,- pnessed gas; discharged into, and confinedin a, receiver such, as is.,c .on 1 mon-lyused with aircompressors to retain the; compressed gas .afiter it worksnormally, as hereinafiten deiscrgibed Thetheoretieali Wonk consumed in one: stroke by thecon pnession 0E air in this manner firom a, given, absolute.v pressureto a stated-higher pressureandits discharge. finom, the cylinder; isdiagrammati cally represented ,in Figs, 5; and. 6, the. lowest pressune, being oneand the highest pressure being four atmospheres, the stroke displa ement being. a, unit of volume, the compression. being, per- Lformed in. two stages, and. the intermediate "pnessureat the. end of the first stage. being ,two. atm osph,enes. In Fig. 6- the line 12 represents the stnoke displacement; of the. piston; 10, the arbitrary clearan ce, connected with the. glow-pressure space; 01-, thevohume inducted totheloyv-pressurespace; "0, UhfiVOl-lljllGdiS- charg nd e 9- it thewron e pendedin compnessingthevolumer to thevolu me ei and dischargingthe latter firom the l;o.w-

'0 represents the. stnokedisplaeement; m, theclearance connected with the high-pressure spaceand, computed as herein specifiedp'v the voluzrne. discharged, firom the low-pressure space, which, is also. the volume, inducted to the high-pressure space o the-volume dis,-

Echarged' after the second stage, ofi compresexpa-nsion and close at the same place where 1 space. When/the pistonli-n this stroke reaches is expelled fro nthat sideexcept what fills thev soon annives at. the maximum pressure, thev machi ne. becomes fully, charged, and te- ,pressure spaceiintozthe passagewhieh leads ,tothe.high-pressunespace, In, Fig. 5,the line llO sion, and the area It Z Win the work expended in making the final stage of compression and in efiecting the discharge of the changed volume out of the cylinder. The sum of these two areas fg 72. 7c and h Z 717, n represents the total work of compressing the volume Q1 adiabatically under the specified conditions. In practice of course the work of overcoming the passive resistances of frictions would be added to the amount of the work represented. The total theoretical exterior work performed in expandinga VOlUlI16U dOWH tooneatmosphere from four atmospheres is also indicated by the sum of the areasfg h and h Z m 11.

Stage expansion or compression may also be partly carried out in a cylinder constructed as I have described and partly in an ordinary single expansion or compression engine. An example of such construction is shown in Fig. 3. In this arrangement the cylinder 1 is the high-pressure cylinder, constructed, as hereinbefore described, with clearance-chambers 7 in the head 4. In expanding the gas exhausts from the low-pressure space of the cylinder 1 through the valve 19 into the chest 20. Thence it is alternately inducted to the ordinary double-acting engine-cylinder 22 through the valves 21, expanding equally 011 both sides of the piston 23, exhausting into the common exhaust-chamber 22, and finally passing out at the opening 25. This arrangement provides a means of compressing or expanding through three stages in two cylinders when the operation is carried out in one of said cylinders. In this case the low-pressure cylinder may sometimes be smaller than the high-pressure cylinder when the ratio of change of pressure and volume in the highpressure cylinder is small as compared with the ratio of such change in the low-pressure cylinder.

By arranging two engine-cylinders c011- structed in accordance with my invention in such manner that their piston-rods cooperate with a single fly-wheel shaft and so that the low-pressure space of the cylinder inducting at higher pressure exhausts into the high-pressure space of the cylinder inducting at a lower pressure I can effect a quadruple stage expansion with said two cylinders.

By the use of three cylinders constructed in accordancewith my invention and similarly connected I effect a seXtuple compression or expansion. By the use of two such cylinders and one of the ordinary type I can effect a quintuple compression or expansion.

What I claim as my invention is- 1. As a means for changing, in diiferent stages, the volume and pressure of a gas or vapor, an engine-cylinder containing a reciprocating piston and having equal piston displacement in both a high-pressure space on one side of the piston and a low-pressure space on the opposite side of the piston, the said cylinder having an end clearance connected with its high-pressure space larger than that connected with its lowpressure space, said high and low pressure spaces having between them a connecting-passage and said larger end clearance being a mathematical function of the end clearance connected with said low-pressure space and computable therefrom, substantially as and for the purposes specified.

2. As a means for changing in stages th volume and pressure of a gas or vapor, the combination with an engine-cylinder con taining a reciprocating piston and having equal piston displacement in both a highpressure space on one side of the piston and a low-pressure space on the opposite side thereof and an end clearance connected with its high-pressure space larger than that connected with its low-pressure space, said high and low pressure spaces having between them a connecting-passage and said larger end clearance being a mathematical function of the clearance connected with said lowpressure space and computable therefrom substantially as described, of means for varying the said largerend clearanceindependently of the position of the cylinder-head adjacent to said high-pressure space, substantially as and for the purposes described.

3. The combination with an engine-cylinder containing a reciprocating piston and having a uniform piston displacementin both a high-pressure space on one side of the piston and a low-pressure space on the opposite side of the piston, the said cylinder having an end clearance connected with the highpressure space larger than that connected with the low-pressure space, said high and low pressure spaces having between them a valve controlled connecting passage, of means for varying end clearance independently of the position of the cylinder-head adjacent to said clearance, substantially as herein described.

4. As a means for changing in stages the volume and pressure of a gas or vapor, the combination with an engine-cylinder containing a reciprocating piston that has equal piston displacement in both a high-pressure space on one side of the piston and a lowpressure space on the opposite side of the piston, the said cylinder having an end clearance connected with its high-pressure space larger than that connected with the low-pressure-space, said high and low pressure spaces having between them a connecting-passage and said larger end clearance beinga mathematical function of that connected with said low-pressure space and computable therefrom substantially as described, of means for varying and adjusting the volume of said larger end clearance to any fraction of the stroke displacementwithin the limits of maximum and minimum end clearance for which,

said cylinder is designed, substantially as and for the purposes set forth.

5. As a means for changing, in difierent stages, the volume and pressure of a gas or vapor, an engine-cylinderoontaininga reciprocating piston and having equal piston displacement in both a high-pressure space on 5 one side of the piston and a low-pressure space on the opposite side of the piston, the said cylinder having an; end clearance con-'- nect-ed with its high-pressure space larger than that connected with its low-pressure TO space, said high-pressure and low-pressure spaces being connected with each other by a valve-controlled passage, substantially as and for the purposes specified.

Signed-at NewYork, in: the county of New York and State of New York, this 23d day of 15 March, A. D, 1899.

LEICESTER ALLEN.

Witnesses:

A. ALLEN, Mrs, E. NEWTON. 

